1. Field of the Invention
The present invention relates to a radio base station/radio base station controller (hereinafter referred to as a base station) for carrying out radio communication with a mobile station, a mobile station, and a state control method of those, and particularly to a base station, a mobile station, and a state control method of those, in which setting of an inactivity timer value is dynamically changed according to a use state to decrease an unused time of a radio channel in a non-communication time in which transmission/reception of data is not carried out and to improve the use efficiency of the radio channel. Incidentally, the inactivity timer value is, as described below, a value for determining the timing when a radio channel disconnection processing for changing a connected state to a dormant state is started (see a document “cdma 2000 High Rate Packet Data Air Interface Specification, 3GPP2 C. S0024 Version 2.0, Oct. 27, 2000”).
2. Description of the Related Art
From the development of a recent digital mobile communication system, radio packet data communication services have been provided in addition to voice communication services. In the radio packet data communication services, a user accesses a server apparatus through a base station, an internet network and the like, so that exchange of E-mail, browse of Web information, and the like can be carried out anytime and everywhere. However, communication resources used for radio communication, for example, frequency resources are finite, and in order to provide services to the most possible subscribers by the finite frequencies, it is very important to disconnect a radio channel in which transmission/reception of data is not carried out and to assign it to another user.
In the radio packet data communication, as disclosed in a document “Data Service Options for Spread Spectrum Systems: cdma2000 High Speed Packet Data Service Option 33, PN-4692.12 (TIA/EIA/IS-707-A-2.12), January 2000”, there are a “connected state” and a “dormant state” as a state of transmission/reception of a packet. The “connected state” is a state in which a radio channel is connected between a base station and a mobile station. On the other hand, the “dormant state” is a state in which a call is brought into a suspended state and the radio channel is temporarily disconnected between the base station and the mobile station. In general use environment of the radio packet data communication, there are few cases where packets are always transmitted and received between the base station and the mobile station, and the packets are normally intermittently transmitted and received. Then, a method is adopted in which if the packet is not transmitted and received for a definite time in the connected state, the state is forcibly changed to the dormant state. For that purpose, a timer called an inactivity timer which starts to count up from the completion of packet transmission/reception is set, and in the case where new transmission/reception is not carried out in a timer set time, the state is changed to the dormant state. An inactivity timer value as a timer for changing the connected state to the dormant state is calculated on the basis of the system architecture, the traffic amount and the like, and a specific fixed value is not regulated. The above document suggests that the inactivity timer value is not set to a value of 20 seconds or less.
Besides, in general, in the radio communication, while a mobile station continues communication (connection of a radio channel), switching of a base station under communication (hand-over) is carried out. Thus, the number of mobile stations in a cell managed by a certain base station becomes fluent. Besides, since the frequency resources are finite, in order to provide services using a radio channel for many subscribers, it is necessary to assign the radio channel to the most possible users. Then, by setting the inactivity timer, the radio channel in which transmission/reception of data is not carried out is temporarily disconnected, and the radio channel is temporarily assigned to another mobile station requiring transmission/reception of data, and as a result, the radio channel can be efficiently used.
In the prior art, a fixed value is used for the set value of the inactivity timer irrespectively of the type of data to be transmitted and received. However, a transmission interval is varied according to the type of data. Thus, in the case where the set value of the inactivity timer is made the fixed value, unless the inactivity timer value is suitably set according to a traffic amount in such a manner that it is set to be short when data such as E-mail having a small size and taking a short communication time is intermittently transmitted and received, and it is set to be long when data such as stream data having a large size and taking a considerable communication time is divided into packets and is transmitted and received, there is a problem that surplus processing due to connection/disconnection of the radio channel is increased, and the use efficiency of the radio channel is lowered.
In the case where hand-over is carried out with the movement of a mobile station while a radio channel is connected, as compared with the case where the movement is made without connection of the radio channel, the processing amount of the mobile station/the radio base station/the radio base station controller is increased. This is because in the movement at the time when the radio channel is not connected, only the position registration information is transmitted from the mobile station to the radio base station/the radio base station controller, whereas if the radio channel remains connected, in order to maintain the radio channel, an exchange between the mobile station/the radio base station/the radio base station controller occurs. Thus, it is necessary to suitably set the inactivity timer value according to the traffic amount, for example, the radio channel of the mobile station in which the traffic amount is small is disconnected rather early.
As means for solving the above problem, it is also conceivable that the fixed value of the inactivity timer is calculated from a past traffic amount etc. in a certain cell. However, as long as the fixed value of the inactivity timer is used, the above problem always remains.